Evidence that androstadienone, a putative human chemosignal, modulates women's attributions of men's attractiveness

Considerable research effort has focused on whether specific compounds found within human body odor influence the behavior or physiology of other individuals. The most intensively studied is 4,16-androstadien-3-one, a chemical which is known to modulate mood and have activational effects in the sympathetic nervous system in a context-dependent manner, but whose action in mate-choice contexts remains largely untested. Here we present evidence that this androgen steroid may modulate women's judgments of men's attractiveness in an ecologically valid context. We tested the effects of androstadienone at a speed-dating event in which men and women interacted in a series of brief dyadic encounters. Men were rated more attractive when assessed by women who had been exposed to androstadienone, an effect that was seen in two out of three studies. The results suggest that androstadienone can influence women's attraction to men, and also that research into the modulatory effects of androstadienone should be made within ecologically valid contexts.

Women's preferences for masculinity in male faces are highest during reproductive age range and lower around puberty and post-menopause

Masculinity in male faces is thought to be a sign of mate quality and is associated with measures of long-term health. Previous studies have demonstrated that women's masculinity preferences change across the menstrual cycle with women preferring more masculine men during phases of the menstrual cycle where fertility is highest (i.e. the late follicular phase). Given the hormonal correlates of such preferences and that these hormones change across the life span, we tested for differences in female masculinity preferences at different ages. We compared the masculinity preferences of peri-pubescent girls and young adult women (Study 1), circum-menopausal women reporting to either be pre- or post-menopause (Study 2), and a large sample of women across a wide range of ages (Study 3). In all three studies, preferences for masculinity in male faces were highest in women who were at a reproductively active age. Preferences for masculinity were lower when females were peri-pubescent, post-menopausal, or at ages corresponding to these groups. These data support the notion that masculinity in male faces is an important trait for reproductively relevant mate choice decisions. These data also highlight a shift in female visual preferences for men that is associated with important stages of the lifespan. Visual preferences appear to track important hormonal changes associated with age; as women pass puberty their preferences shift towards facial traits associated with mate quality and as women undergo menopause their preferences for such facial traits decrease. Overall, these results demonstrate the important role of reproductive status and support the notion that preferences for male faces are tied to reproductively relevant hormones.

Olfaction scaffolds the developing human from neonate to adolescent and beyond

The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

A lover or a fighter? Opposing sexual selection pressures on men's vocal pitch and facial hair

Men’s optimum masculinity depends on whether they want to attract partners or compete with rivals. We found that men’s voice pitch was most attractive around 1.5 standard deviations lower than average, whereas facial hair growth did not consistently affect attractiveness. In contrast, men were perceived ever more dominant with lower voices and more facial hair. Sexual selection consists of both attracting mates and competing against rivals, but here selection pressures might oppose each other somewhat.

The traditional assumption within the research literature on human sexually dimorphic traits has been that many sex differences have arisen from intersexual selection. More recently, however, there has been a shift toward the idea that many male features, including male lower-pitched voices and male beard growth, might have arisen predominantly through intrasexual selection: that is, to serve the purpose of male–male competition instead of mate attraction. In this study, using a unique set of video stimuli, we measured people’s perceptions of the dominance and attractiveness of men who differ both in terms of voice pitch (4 levels from lower to higher pitched) and beard growth (4 levels from clean shaven to a month’s hair growth). We found a nonlinear relationship between lower pitch and increased attractiveness; men’s vocal attractiveness peaked at around 96 Hz. Beard growth had equivocal effects on attractiveness judgments. In contrast, perceptions of men’s dominance simply increased with increasing masculinity (i.e., with lower-pitched voices and greater beard growth). Together, these results suggest that the optimal level of physical masculinity might differ depending on whether the outcome is social dominance or mate attraction. These dual selection pressures might maintain some of the documented variability in male physical and behavioral masculinity that we see today.

Current issues in the study of androstenes in human chemosignaling

We review research on the 16-androstenes and their special claim, born originally of the finding that androstenes function as boar pheromones, to be human chemosignals. Microbial fauna in human axillae act upon the 16-androstenes to produce odorous volatiles. Both individual variation and sex differences in perception of these odors suggest that they may play a role in mediating social behavior, and there is now much evidence that they modulate changes in interpersonal perception, and individual mood, behavior, and physiology. Many of these changes are sensitive to the context in which the compounds are experienced. However, many key outstanding questions remain. These include identification of the key active compounds, better quantification of naturally occurring concentrations and understanding how experimentally administered concentrations elicit realistic effects, and elucidation of individual differences (e.g., sex differences) in production rates. Until such issues are addressed, the question of whether the androstenes play a special role in human interactions will remain unresolved.

Body odor quality predicts behavioral attractiveness in humans

Growing effort is being made to understand how different attractive physical traits co-vary within individuals, partly because this might indicate an underlying index of genetic quality. In humans, attention has focused on potential markers of quality such as facial attractiveness, axillary odor quality, the second-to-fourth digit (2D:4D) ratio and body mass index (BMI). Here we extend this approach to include visually-assessed kinesic cues (nonverbal behavior linked to movement) which are statistically independent of structural physical traits. The utility of such kinesic cues in mate assessment is controversial, particularly during everyday conversational contexts, as they could be unreliable and susceptible to deception. However, we show here that the attractiveness of nonverbal behavior, in 20 male participants, is predicted by perceived quality of their axillary body odor. This finding indicates covariation between two desirable traits in different sensory modalities. Depending on two different rating contexts (either a simple attractiveness rating or a rating for long-term partners by 10 female raters not using hormonal contraception), we also found significant relationships between perceived attractiveness of nonverbal behavior and BMI, and between axillary odor ratings and 2D:4D ratio. Axillary odor pleasantness was the single attribute that consistently predicted attractiveness of nonverbal behavior. Our results demonstrate that nonverbal kinesic cues could reliably reveal mate quality, at least in males, and could corroborate and contribute to mate assessment based on other physical traits.

Changes in Women's Facial Skin Color over the Ovulatory Cycle are Not Detectable by the Human Visual System

Human ovulation is not advertised, as it is in several primate species, by conspicuous sexual swellings. However, there is increasing evidence that the attractiveness of women's body odor, voice, and facial appearance peak during the fertile phase of their ovulatory cycle. Cycle effects on facial attractiveness may be underpinned by changes in facial skin color, but it is not clear if skin color varies cyclically in humans or if any changes are detectable. To test these questions we photographed women daily for at least one cycle. Changes in facial skin redness and luminance were then quantified by mapping the digital images to human long, medium, and shortwave visual receptors. We find cyclic variation in skin redness, but not luminance. Redness decreases rapidly after menstrual onset, increases in the days before ovulation, and remains high through the luteal phase. However, we also show that this variation is unlikely to be detectable by the human visual system. We conclude that changes in skin color are not responsible for the effects of the ovulatory cycle on women's attractiveness.

Measurement equivalence between men and women in the abbreviated Social and Emotional Loneliness Scale for Adults (SELSA)

Health practitioners, policy-makers, and psychologists point to legitimate concerns about the negative impact of loneliness. To help resolve such negative impact, we need to better understand the psychometric structure of loneliness. Men’s and women’s differing social roles may mean that they experience different sources of loneliness. After matching via exact matching, we compared men and women’s scores (N = 273) on the abbreviated form of the Social and Emotional Loneliness Scale for Adults (SELSA) using confirmatory factor analysis and measurement invariance testing. We replicated the three-factor structure of the SELSA, thereby providing further evidence for differing etiologies of family, romantic, and social loneliness. We found no good evidence for gender differences in the structure of the questionnaire answers, indicating that the SELSA can be used to further illuminate the implications of loneliness for men and women.

Hungry people prefer larger bodies and objects: The importance of testing boundary effects

Several lab-based studies have indicated that when people are hungry, they judge larger women's bodies as more attractive, compared to when they are satiated. These satiety-dependent judgements are assumed to provide explanatory power when it comes to the noted cross-cultural differences in attitudes towards women's adiposity, whereby people who live in regions that are under greater nutritional stress tend to have more favourable attitudes towards bigger bodies. However, it is premature to assume that women's bodies are the proper or actual domain of the satiety-dependent judgement shifts found within research study testing contexts until stimuli other than female bodies have also been tested: The research programme falls into the trap of confirmation bias unless we also seek out disconfirmatory evidence and test the boundaries of the effects of hunger. Accordingly, we collected attractiveness judgements of female and male bodies manipulated to vary in size by varying level of adiposity, and objects manipulated to vary in size, from 186 participants who also reported their current hunger level. We found that larger sizes of stimuli in general, and women's bodies in particular, especially when judged by women, were judged as more attractive by the hungrier participants. We discuss these patterns in the context of the Insurance Hypothesis, the Environmental Security Hypothesis, and the impact of hunger on acquisition.

Jealousy as a Function of Rival Characteristics: Two Large Replication Studies and Meta-Analyses Support Gender Differences in Reactions to Rival Attractiveness But Not Dominance

Jealousy is a key emotion studied in the context of romantic relationships. One seminal study (Dijkstra, P., & Buunk, B. (1998). Jealousy as a function of rival characteristics: An evolutionary perspective. Personality and Social Psychology Bulletin, 24 (11), 1158-1166. https://doi.org/10.1177/01461672982411003) investigated the interactions between a participant's gender and their reactions to the attractiveness or dominance of a romantic rival. In a vignette-based study, it was found that women's jealousy was more responsive than men's to a rival's attractiveness, whereas in contrast, the rival's dominance evoked more jealousy from men than from women. Here, we attempt to replicate these interactions in two samples (N = 339 and N = 456) and present subsequent meta-analyses (combined Ns = 5,899 and 4,038, respectively). These meta-analyses showed a small, significant effect of gender on jealousy provoked by rival attractiveness, but no such response to rival dominance. We discuss the potential reasons for these findings and future directions for research on jealousy and rival characteristics.

Are we measuring loneliness in the same way in men and women in the general population and in the older population? Two studies of measurement equivalence

BACKGROUND

High levels of loneliness are associated with negative health outcomes and there are several different types of interventions targeted at reducing feelings of loneliness. It is therefore important to accurately measure loneliness. A key unresolved debate in the conceptualisation and measurement of loneliness is whether it has a unidimensional or multidimensional structure. The aim of this study was to examine the dimensional structure of the widely used UCLA Loneliness Scale and establish whether this factorial structure is equivalent in men and women.

METHODS AND SAMPLE

Two online UK-based samples were recruited using Prolific. The participants in Study 1 were 492 adults, selected to be nationally representative by age and gender, whilst the participants in Study 2 were 290 older adults aged over 64. In both studies, participants completed the UCLA Loneliness Scale (Version 3) as part of a larger project.

RESULTS

In both studies, the best fitting model was one with three factors corresponding to 'Isolation,' 'Relational Connectedness,' and 'Collective Connectedness.' A unidimensional single factor model was a substantially worse fit in both studies. In both studies, there were no meaningful differences between men and women in any of the three factors, suggesting measurement invariance across genders.

CONCLUSION

These results are consistent with previous research in supporting a multidimensional, three factor structure to the UCLA scale, rather than a unidimensional structure. Further, the measurement invariance across genders suggests that the UCLA scale can be used to compare levels of loneliness across men and women. Overall the results suggest that loneliness has different facets and thus future research should consider treating the UCLA loneliness scale as a multidimensional scale, or using other scales which are designed to measure the different aspects of loneliness.

Consistency of Eye Coloration Across Different Relationship Partners

Studies have indicated that people are attracted to partners who resemble themselves or their parents, in terms of physical traits including eye color. We might anticipate this inclination to be relatively stable, giving rise to a sequential selection of similar partners who then represent an individual's "type". We tested this idea by examining whether people's sequential partners resembled each other at the level of eye color. We gathered details of the eye colors of the partners of participants (N = 579) across their adult romantic history (N = 3250 relationships), in three samples, comprising two samples which made use of self-reports from predominantly UK-based participants, and one which made use of publicly available information about celebrity relationship histories. Recorded partner eye colors comprised black (N = 39 partners), dark brown (N = 884), light brown (N = 393), hazel (N = 224), blue (N = 936), blue green (N = 245), grey (N = 34), and green (N = 229). We calculated the proportion of identical eye colors within each participant's relationship history, and compared that to 100,000 random permutations of our dataset, using t-tests to investigate if the eye color of partners across an individual's relationship history was biased relative to chance (i.e., if there was greater consistency, represented by higher calculated proportions of identical eye colors, in the original dataset than in the permutations). To account for possible eye color reporting errors and ethnic group matching, we ran the analyses restricted to White participants and to high-confidence eye color data; we then ran the analyses again in relation to the complete dataset. We found some limited evidence for some consistency of eye color across people's relationship histories in some of the samples only when using the complete dataset. We discuss the issues of small effect sizes, partner-report bias, and ethnic group matching in investigating partner consistency across time.